[Caddylackn]

If you are trying to drive as efficiently as possible, even a two second delay is too much.

I drive a new Rav4 Hybrid at work sometimes. That has 1 minute intervals, but it keeps the last ten minutes as a bar graph on the screen. It will show a trend, but unless you are on a constant grade and speed for a full minute, it is pretty useless. The Rav4 Hybrid is a nice car. I can get 50 mpg on flat ground between 55 - 60 mph.